The great importance of mosquitoes lies in their role as transmitters of pathogens and parasites, and in their use as experimental animals well suited to laboratory investigations into aspects of biochemistry, physiology and behaviour. The largest part of this latest volume of The Biology of Mosquitoes concerns interactions between mosquitoes and viruses and the transmission of arboviruses to their vertebrate hosts, while the remainder concerns symbiotic interactions between mosquitoes and bacteria. The introduction provides a timely review of the first major development in mosquito taxonomy for several decades. Further chapters describe the interactions between mosquitoes and the viruses that infect them, the transmission and epidemiology of seven very important arboviruses, and the biology of bacteria that are important control agents or of great biological interest. Like the earlier volumes, Volume 3 combines recent information with earlier important findings from field and laboratory to provide the broadest coverage available on the subject.